Research in non-equalization machining method for spatial cam

Many kinds of devices with cam have been widely used in various mechanical equipments. However, non-equalization machining for spatial cam trough remains to be a difficult problem. This paper focuses on the analysis of running conditions and machining processes of spatial cam with oscillating follower. We point out the common errors in the biased distance cutting. By analyzing the motion of oscillating follower of spatial cam, we present a new 3D curve expansion model of spatial cam trough-outline. Based on this model, we have proposed a machining method for trochoidal milling with non-equalization diameter cutter. This new method has led to a creative and effective way for non-equalization diameter machining for spatial cam with oscillating follower.     

Peer collaboration: the relation of regulatory behaviors to learning with hypermedia

Peer collaboration is a pedagogical method currently used to facilitate learning in classrooms. Similarly, computer-learning environments (CLEs) are often used to promote student learning in science classrooms, in particular. However, students often have difficulty utilizing these environments effectively. Does peer collaboration help students learn with these environments? Little research looking closely at face-to-face peer collaboration with computer learning environments exists. Utilizing a social-cognitive theoretical framework, this study investigated the relation between the conceptual-knowledge learning and the collaborative regulatory behaviors of students working with a peer as they studied about the human circulatory system using a hypermedia CLE. Fifty-four high-school students from the East Coast of the United States were audiotaped to identify the collaborative regulatory behaviors they evidenced as they studied. Results revealed significant correlations among students’ proportion of categories of regulatory behaviors and their learning gains (from pretest to posttest). Moreover, qualitative analyses revealed particular behaviors that larger-gain collaborative pairs engaged in to a greater extent than smaller-gain pairs as they learned with the hypermedia environment.     

Contextual factors that sustain innovative pedagogical practice using technology: an international study

Pedagogical innovation—whether involving technology or not—is shaped by a complex interaction of the innovation with contextual factors such as school and school district policy, leadership, cultural norms and values, teacher attitudes and skills, and student characteristics. This study examined school and classroom contexts in which pedagogical innovations employing technology were successfully sustained. Data were obtained from 59 cases drawn from the Second Information Technology in Education Study—Module 2, a project that examined 174 cases of innovative pedagogical practice in schools in 28 countries. An explanatory model of sustainability was derived from a qualitative analysis of the cases using grounded theory techniques. Essential conditions for the sustainability of classroom innovation were teacher and student support of the innovation, teacher perceived value of the innovation, teacher professional development, and principal approval. Contributing factors for sustainability were supportive plans and policies, funding, innovation champions, and internal and external recognition and support. An interactive website that allows for searching of SITES-M2 case reports on various attributes such as sustainability, transferability, level of school, and evidence of supportive policies and plans is available at http://sitesm2.org.     

Session - 3 December 19, 2007 Cardiovascular risk markers - II

Oral Cancer is one of the five leading sites of cancer in Indian population. The circulating immune complexes were investigated in 100 serum samples of 60 oral cancer patients having different grades of the disease and 40 patients with precancerous lesions obtained from Nair Hospital Dental collage, Mumbai. The results obtained were compared with those of group of 40 healthy blood donors. Elevated levels of Circulating Immune Complexes were observed in oral cancer patients and patients with oral precancerous lesions. 92% positive samples were observed in well differentiated squamous cell carcinoma whereas 100% positive samples were observed in both moderately and poorly differentiated squamous cell carcinoma. Oral leukoplakia and oral submucous fibrosis showed 15% and 90% positivity respectively. Increased level of Circulating Immune complexes in high grade tumor suggest that Circulating Immune complexes is likely to contribute in evaluating the degree of malignancy, but follow up study is needed to draw any conclusion regarding it's prognostic role     

Undergraduates’ learning experience and learning process: quantitative evidence from the East

This article examines the construct validity of the Course Experience Questionnaire (CEQ) in Hong Kong and investigates the similarities and differences in the process of learning among students in different disciplinary studies. It is based on a survey of 1,563 undergraduate students in two disciplines, humanities and sciences, and of principally Chinese ethnicity. Findings from exploratory and confirmatory factor analyses support the scale structure of the four subscales of a modified version of the CEQ (good teaching, clear goals and standards, appropriate work, and appropriate assessment) in a non-Western context and could provide a basis for cross cultural research and international benchmarking. While there was variation across subgroups, there was a genuine pattern of relationships between the perceptions of learning environment and learning strategies shown by structural modeling. This information could be used to inform the design of discipline-specific programs in the new curriculum.     

QTL analysis for some quantitative traits in bread wheat

Quantitative trait loci (QTL) analysis was conducted in bread wheat for 14 important traits utilizing data from four different mapping populations involving different approaches of QTL analysis. Analysis for grain protein content (GPC) sug- gested that the major part of genetic variation for this trait is due to environmental interactions. In contrast, pre-harvest sprouting tolerance (PHST) was controlled mainly by main effect QTL (M-QTL) with very little genetic variation due to environmental interactions; a major QTL for PHST was detected on chromosome arm 3AL. For grain weight, one QTL each was detected on chromosome arms 1AS, 2BS and 7AS. QTL for 4 growth related traits taken together detected by different methods ranged from 37 to 40; nine QTL that were detected by single-locus as well as two-locus analyses were all M-QTL. Similarly, single-locus and two-locus QTL analyses for seven yield and yield contributing traits in two populations respectively allowed detection of 25 and 50 QTL by composite interval mapping (CIM), 16 and 25 QTL by multiple-trait composite interval mapping (MCIM) and 38 and 37 QTL by two-locus analyses. These studies should prove useful in QTL cloning and wheat improvement through marker aided selection.     

Effects on cytotoxicity and antibacterial properties of the incorporations of silver nanoparticles into the surface coating of dental alloys

The aim of this study was to research the changes in cytotoxicity and antibacterial properties after silver nanoparticles (AgNPs) were incorporated into the surface coating of dental alloys. AgNPs were attached to cobalt chromium alloys and pure titanium using a hydrothermal method, according to the reaction: AgNO₃+NaBH₄→ Ag+1/2H₂+1/2B₂H₆+NaNO₃. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity of the alloys when in contact with osteogenic precursor cells (MC3T3-E1) from mice and mesenchymal stem cells (BMSC) from rats. The antibacterial properties of dental alloys incorporating three different concentrations (10, 4, and 2 μmol/L) of AgNPs were tested on Staphylococcus aureus (SA) and Streptococcus mutans (MS). High cytotoxicity values were observed for all dental alloys that contained 0% of AgNPs (the control groups). The incorporation of AgNPs reduced cytotoxicity values. No significant difference was observed for antibacterial performance when comparing dental alloys containing AgNPs to the respective control groups. The results demonstrated that the cobalt chromium alloys and pure titanium all had cytotoxicity to MC3T3-E1 and BMSC and that the incorporation of AgNPs could reduce this cytotoxicity. The concentrations of AgNPs adopted in this study were found to have no antibacterial action against SA or MS.